1. Field of the Invention
This invention relates to peripherals controllers and more specifically to a technique for hot plugging a disk array controller card that combines PCI and SCSI buses on a single connector.
2. Description of the Related Art
Servers are critical components of a computer network as their efficiency and reliability directly impact the efficiency and reliability of the computer network as a whole. Servers have typically been utilized to provide access to shared printers and files. As a general rule, a computer network has multiple file servers which have traditionally been used as storage hubs for various files. In a typical application, a copy of a stored file is transferred to a client on demand with an updated file being returned to the server for storage. As a result of on-demand file transfer, any delay in accessing files on a disk subsystem directly affects the efficiency of the network.
The requirement for high performance efficient networks has led to advances in disk drives and in disk subsystem architectures. Disk drive storage sizes have increased, access times have decreased, and data transfer rates have increased. However, while disk drive technology has advanced, processing capabilities of personal computers and workstations have also advanced. As more clients are added to a given network and the processing capability of those clients increase, there is a continuing push to minimize the downtime (increase the reliability) of disk subsystems servicing that network.
In response to the need for reliable inexpensive disk drive subsystems, redundant array of inexpensive disks (RAID) configurations have been developed. RAID implementations can provide error detection and duplicate storage of information on a disk drive subsystem in the event one or more disk drives in the disk drive subsystem fail. Some of the advantages provided by RAID subsystems have been higher data transfer rates, increased disk capacity, higher input/output (I/O) rates, and faster data access. Depending upon which level of RAID was implemented, disk striping, mirroring, parity checking, or some combination was employed. For example, RAID level 4 implements block interleaved data striping with parity checking, with parity information being stored on a single disk drive. In contrast, RAID level 5 strips both data and parity information across multiple disk drives. These RAID implementations and others are well known to those of ordinary skill in the art.
In an effort to minimize down-time of subsystems servicing a computer network, and in turn the network, hot plugging techniques were developed. A requirement of hot plugging a given peripheral controller card into a computer system is that the mating operation not disturb a host system bus. The ability to hot plug a peripheral controller card into a computer system is highly desirable in computer systems that require continuous operation. File servers are a typical example of computer systems that can benefit from hot plugging since they require virtually continuous operation in providing client access to files. Another technique for minimizing a file server's downtime and increasing the file server's reliability has been to utilize redundant disk array controller cards. In a typical file server, a redundant disk array controller card provides a back-up that can assume control of related disk subsystems should an associated disk array controller card fail.